The present invention relates to data communications in general and, in particular, to adaptive coding and modulation.
Service providers may desire to use communication systems to provide high availability to high-quality services for their subscribers. Typically, conditions differ across regions of the network, for example, due to differences in weather, geography, density of structures, density of data terminals, etc. These different network conditions may result in differences in apparent availability or quality of services to subscribers.
Adaptive communication techniques, like adaptive coding and modulation (“ACM”), may dynamically adjust coding and modulation schemes to adapt to these changing network conditions. For example, as conditions change, the availability of services may be increased or maintained by using more reliable (lower order) coding and modulation schemes. In order to adapt, however, the network may first have to detect information relating to one or more conditions. As such, there may be a delay between a change in network conditions and an adjustment in communications.
In the case of fixed data terminals, link conditions (e.g., network conditions affecting a communication link associated with a data terminal) may typically change relatively slowly. For example, large changes in weather, density of obstacles to the communication, etc. may happen over hours, days, or even longer periods of time. With mobile data terminals, however, link conditions may change much more quickly. For example, as a cellular telephone moves through the network, it may quickly move through large regional differences in network conditions, like mountains, tunnels, different areas of a building, etc. In some cases, these changes in link condition may be too rapid for adaptive techniques to keep up.
Thus, it may be desirable to generate predictions of future link conditions and to dynamically pre-adjust transmission parameters with an awareness of those predicted conditions.